Debt Debt (Consolidated Interest Coverage Ratio) (Details)	3 Months Ended	12 Months Ended
	Oct. 31, 2017	Jul. 31, 2017	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018
Debt Instrument, Covenant Description	5.2
current consolidated interest coverage ratio	193.00%
Debt Instrument, Covenant Compliance	40.6	67.5
Maximum [Member]
required consolidated interest coverage ratio	175.00%		250.00%	175.00%	175.00%
Ferrellgas, L.P. [Member]
Debt Instrument, Covenant Description	5.2
current consolidated interest coverage ratio	193.00%
Debt Instrument, Covenant Compliance	40.6	67.5
Ferrellgas, L.P. [Member] | Maximum [Member]
required consolidated interest coverage ratio	175.00%		250.00%	175.00%	175.00%
Interest Coverage Covenant [Member]
Debt Instrument, Covenant Description	21.1
Debt Instrument, Covenant Compliance	12.1
Interest Coverage Covenant [Member] | Ferrellgas, L.P. [Member]
Debt Instrument, Covenant Description	21.1
Debt Instrument, Covenant Compliance	12.1